To maintain a green environment, graphite rods from spent batteries were recycled to manufacture modified electrodes by poly(o-toluidine) using an eco-friendly electrochemical method. The modified electrode can be used as a sensitive detector of copper ions in drinking water. Generally, copper ions in drinking water are considered toxic when they exist in high concentrations. This electrode could be made portable and reused several times after activation. The graphite electrode extracted from spent batteries was modified using an electrochemical cell containing a solution comprised of (o-toluidine), acetonitrile, and ammonium perchlorate as electrolyte, and hydrochloride acid (HCl 0.2 M) as a dopant. Current density of 1.642 × 10^-3 A.cm^-2 was applied. The modified electrode was characterized using FT-IR, XRD spectroscopes, and scanning electron microscope (SEM). The best activation time was obtained when the modified electrode was soaked in distilled water for 1 hour. The electrode exhibits near Nernstian cationic slope of 28.226 mV/decade and lower limit of detection of 6.78× 10^-6 M with fast response time of 60 s.